This invention relates to guidance systems for farm implements and the like, and more particularly to a guidance system which provides an indication of the position of a farm implement relative to the crop rows to assist the driver in maintaining the implement on a desired course while planting, cultivating or harvesting the crop.
One of the most common methods of weed control in agriculture today is mechanical cultivation. To control weeds in row crops, a row cultivator is used. Driving a row cultivator is a very tedious job. Cultivating row crops requires the operator's full concentration to avoid plowing out the crop instead of the weeds. Cultivating for many hours is physically tiring to the eyes as well as the body because the operator must usually assume an unnatural position to see the rows while operating the tractor at the same time. This process has been further complicated in recent years by the adoption of the rear mounted cultivator. Because this type of cultivator is attached to the rear of the farm tractor and is therefore out of the operators normal field of vision, the operator must use some reference other than the actual cultivator to determine his position on the row. The most common reference is a rod suspended from the front axle or side of the tractor and positioned over a row. The operator tries to keep the rod centered over the row with the probability that the rear mounted cultivator will follow.
Many problems arise from using the above technique of guiding a rear-mounted cultivator. This method works well when the rows are straight, but guiding a cultivator in this way is difficult when rows curve. When the rear mounted cultivator is used to cultivate row crops planted on uneven terrain, the rear mounted cultivator tends to drift downhill even though the tractor maintains its position over the row. In cultivator applications, if the cultivator drifts so that one row is off, all of the rows will be off. Unevenness, or changes in soil conditions can cause a rear-mounted cultivator to pull to one side, resulting in plowing out of the crop.
Another consideration is that more and more farmers are using tractors equipped with cabs for reasons of both health and comfort. Most modern tractor cabs restrict the field of vision of the operator even more. As cultivators become larger and wider, accurate control becomes more difficult.
One known guidance control system for a cultivator employs twin probes or discs following a mark or furrow, or guide rods which sense from the crop itself to generate electronic signals indicative of deviation of the cultivator from the desired course. The electronic signals are applied to hydraulically operated steering coulters to maintain the cultivator on course. A display unit in the tractor cab includes a row of light emitting diodes which display the direction from center and magnitude of correction being made by the steering coulters. Only one light emitting diode is lighted at a time. An override control allows the operator to turn the steering coulters either direction from center to compensate for unusual side drifts such as would be encountered while operating on a side hill.
This guidance system provides automatic compensation, steering of the cultivator as a function of the error signal generated by the row position sensor. The visual display indicates to the tractor operator the correction being made by the steering coulters rather than a steering correction to be made by the driver of the tractor. Because the light emitting diodes flash on and off with deviation of the cultivator from the desired course, the display provided is both confusing and distracting to the operator. Moreover, the resolution of the amount of deviation displayed is dependent upon the number of light emitting diodes employed.